Kelp beds are highly productive nearshore habitats that support commercial and sport fish, invertebrates, marine mammals and marine birds. Many factors, both natural and anthropogenic, affect the extent and composition of kelp beds. For example, elevated water temperature and intense sea urchin grazing can decimate kelp beds. El Nino events stress kelp by producing several winter storms and reducing upwelling events, which normally replenish the nutrients in the water column. Human influences on kelp beds include sewage and other runoff that decrease water quality and reduce light in the water column. Human activity can also lead to changes in substrate size, which can either increase or decrease available kelp habitat. Kelp plants can be physically damaged by boat propellers and fishing gear. Commercial harvest is not a significant factor of concern in Washington State due to a law prohibiting this practice.

The Nearshore Habitat Program has monitored changes in the areal extent of kelp canopies along the outer coast and the Strait of Juan de Fuca since 1989. Two species of canopy-forming kelp are monitored: Bull kelp (Nereocystis luetkeana) and giant kelp (Macrocystic integrifolia). Results can be viewed or downloaded at: